What Brexit will cost Britain: More debt, weaker growth and a final bill

Brexit is happening. And it will be expensive.

The U.K. is officially leaving the European Union. While those campaigning for more sovereignty and tighter border controls rejoice, the government's own economic forecasters are warning of tough times ahead.

Divorce from the EU will be costly and it could weigh on Britain's economic prospects for years to come.

Here is why:

Weaker growth

The Office for Budget Responsibility, the U.K.'s independent fiscal watchdog, is forecasting growth of 2% in 2017. Prior to the Brexit vote last year, it expected growth of 2.2%.

The downgrade is even bigger for next year. The OBR expects growth of 1.6% in 2018, compared with its pre-Brexit forecast of 2.1%.

Slower job creation

The uncertainty surrounding Brexit is likely to hit jobs too. Private sector hiring confidencefell to its weakest level in three years, according to a survey by the ManpowerGroup published this month. The group asks managers about their hiring plans for the upcoming quarter.

Some companies will need to shift jobs abroad to safeguard their European operations. Major banks have already started this process, announcing the relocation of thousands of jobs.

The OBR expects the number of people claiming unemployment benefit to reach 830,000 this year, 50,000 more than it forecast in March 2016. That number will rise to 880,000 by 2020, roughly 10,000 more than it forecast before the Brexit vote.

It expects unemployment to rise gradually from 2018 and peak at 5.2% in 2020.

Divorce bill

EU countries pay into a shared multi-year budget to finance things like infrastructure projects, social programs, scientific research and pensions for EU bureaucrats.The budget runs until 2020 and EU officials have said they expect the U.K. to honor its commitments even as it leaves the bloc in 2019.

EU Commission President Jean-Claude Juncker said the U.K. will be expected to pay roughly £50 billion ($62.4 billion) to settle its bill.